We used Jen with Sassy Designs as well. The invitations are gorgeous, exactly what we wanted. She was really great about making the changes we asked for. They were affordable, a little over $3 or so per invite, and we could order just the amount we needed, which saved us a lot of money, because there was no minimum. I'm thrilled with them, and we've received many wonderful compliments.
That said, I agree with the poster who said she sometimes takes a little longer than you'd like to get back to you. I think though, you can over come this if you start really early, and really stay on top of it. In the end, I ordered my own envelopes because she said it would be faster, and I ended up being happy with that because I found ones that matched perfectly.. the stardreams line at cutcardstock.com - and they sell on ebay under customcardstock, mars and opal were our colors.
The invites arrived 2 weeks later than I wanted them to. I stayed up till 3 in the morning putting them all together the day they came, so they could be in the next day's mail. I printed the addresses on clear labels I got from Staples, because I couldn't wait any longer to have calligraphy done.
I will say, I'm a type A person.. I fret over everything, so please take my comments with that in mind. All in all, I truly love my invitations, they are exactly what we wanted, and I am glad we went with Jen.
We had looked at Impressions to, and decided against them because of the cost.
For SRUAlum, the Disney ones on Now and Forever are Carlson Craft stock invitations, they have a dozen or so different designs to choose from. You can go to hallmark or the party store to see them in person, they have samples in big books so you can look and feel them. You can buy them in several places online, including ebay and mousesavers, choose your design, fill out the form with your text, choose your font and text color, and they will print them up and send them to you. I think Carlson Cards actually does the printing and sending to you. We looked at these too, most of them have a minimum of 100 and the way each piece is sold separately (invite, envelope, rsvp card) made them too expensive, plus we didn't need anywhere near 100! The ones from Jen/Sassy Design and Impressions, the actual design of the whole invite is custom, not just the text.
--h
Sometimes she takes a little longer than I would like to get back to me, but her designs are just beautiful. 
My invites are just beautiful, exactly what I wanted...
Just mention to her that Angela told you how wonderful she is....
