We have the Platinum Keurig ($179.99 at BB&B, not sure what it is elsewhere). We registered for it for our wedding in September and received it along with a few variety packs from my BIL/SIL. We loooooove it. It was DH's one item he HAD to have when we registered. I didn't really think I'd love it that much but I use it much more than DH. I also have loved trying different kinds- with some of the BB&B GC's we received I have bought some other flavor varieties.
I can't speak for the Tassimo except in that I see k-cups everywhere and only saw a very small section at BB&B for Tassimo. It just doesn't have the popularity that Keurig has, and therefore there's less available. I like that I can buy kcups at the grocery store, at Costco, at BB&B (w/ my 20% off coupons) or at Kohls when I get 30% off coupons. Yes they're more expensive than bulk coffee but you're paying for convenience and it's cheaper than Starbucks or even Wawa (or anywhere that you'd buy coffee out).
We also have the insert that allows you to use your own bulk coffee since I had some leftover from before and I don't mind using that.
There are some varieties I've tried that seem weak at the largest cup size (11ish oz) but there are others that are quite strong. I think it's finding the right k-cup varieties for you.
I had read complaints about the Keurig taking a long time but I haven't found that with ours at all. The brewing is almost immediate.
