Zackiedawg -- I like the description of the a300 and a350 but the highest ISO setting for best quality pics that I've seen in reviews is 400 and that's not better than the H5. Do you find that you get better pics at higher ISO settings than your H5?
I love my H5 - a great camera and I really grew with it, including selling my first photos with it and publishing my first photos with it...so I've got no complaints. However, at higher ISO, the A300 is in a 100% different league - as is any DSLR. Don't read too much into technical reviews that judge the high ISO performance of DSLRs against a benchmark DSLR, viewed at 100% viewable and looking for the differences. I've seen and heard the same lines, that ISO400 was the reasonable limit, and 800 was pushing it, with the Alphas. If you compare with mid-market or semi-pro DSLRs...it won't look as good; compare to base DSLRs, it's about the same; compared to any P&S camera at all - and it's orders-of-magnitude better.
I also routinely shoot ISO800 & 1600, and push to ISO3200 if needed, without fear. With my H5, I'd push to 800 in emergencies, but the results were poor and needed lots of work. I've got lots of examples in my galleries at high ISO...but here's a few ideas:
ISO1600:
And not always with a low light lens...here's ISO800 at full zoom (250mm) on the 18-250 lens, handheld indoors:
And here's ISO 1600 with the 18-250:
Again with the 18-250 lens...this was at ISO3200, which is the maximum ISO for the A300. I still consider this plenty usable, and far far better than I could get at ISO1000 from the H5:
Low light is where all DSLRs have a supreme advantage...even moreso when paired with a proper low light lens. Can other DSLRs do better? Absolutely. But all of them will do better than P&S cams...no contest. It just depends on how important that kind of photography is to you. I didn't really feel any limitations with my H5 for at least 2 years - as I learned more and more how to control the camera and tailor the shots the way I liked. Only then did I find myself pushing up to ISO800 or 1000, and wishing I could get clean results without all the detail loss...or thinking about taking candids or portraits handheld at night or indoors, which required faster shutter speeds in low light - high ISO being the only solution. I also found myself getting deeper into bird and wildlife photography, and needing more burst speed, focus speed, and tracking focus.
Also, is it much heavier? I was looking at the 18-250 lens thinking I could keep that on for the most part. I was quizzing someone I know with a Nikon D50 and he has a similar lens and he says he doesn't change lenses much.
It's definitely heavier. Even the smallest of DSLRs will be significantly heavier than the H5...even without a lens. Once you attach a decent versatile lens like the 18-250, the weight will be 4-5x what you have with the H5. And the size is nearly double - several inches larger in every dimension. And noisier - remember that DSLRs have a fairly noticable mirror-slap noise when snapping a shot, compared to the small electronic shutter noise of the H5, which can even be turned off for full silent mode.
With a versatile lens like the 18-250, you can if you choose make it a 1-lens option...pretty much keeping it on the camera all the time. There are those who would argue that it defeats the purpose of a DSLR by not taking advantage of the interchangeable lenses...but the same argument could be made for those who use their DSLRs in auto mode. It's personal choice. However, even if you think you're going to pick a lens and stick with it, the lens lust bug usually bites, and you find yourself wanting more lenses that can do special things. I knew I had to have more than 1 lens - I purchased my A300 along with 2 other lenses right off the bat - the 18-250 and the 200-500. I also knew I'd want to pick up a F1.4-1.7 low light lens at some point, which I did about a month later. I do keep the 18-250 on the camera most of the time though...the F1.7 goes on when I am planning on shooting low light or night ahead of time, and the 200-500 goes on when I am specifically out on a wildlife shoot. The 18-250 is my compact and convenient travel lens, all-purpose lens, spontaneous lens, and any other time lens.
Sorry for the long answer and samples - feel free to take a look in my galleries - you'll notice one gallery called "introducing the Sony DSLR-A300", which has hundreds of photos in it - but there are some labeled specifically within the gallery as high ISO samples and tests. I don't consider the Alpha the best DSLR at low light, but it does quite well and meets my needs, and offers some other nice advantages that sold me on it over other brands (namely in-body stabilization, easy live view option, flip-out LCD, great battery life, and fairly cheap and abundant backlog of Minolta lenses that are compatible with it).