Last year I used H&R Block's online filing and it worked very smoothly. It lets you save and come back to you taxes later, outputs your copy in PDF format, etc., etc., etc. Federal and state worked fine. I can't remember it all, but I am going to use it again this year. Worked fine in IE 5.1 on the Mac.
We used to buy a copy of Kiplinger's Tax Cut every year (which is made by H&R Block) and this online deal was very familiar and I think easier to use.
I've used TT-web a couple times, overall good experiences, just like mdnky said about H&R, TT-web let's you save and come back, and output in PDF, federal, state. I don't recall which browser on which OS I did it though, probably IE 5 on OSX.
I used TurboTax.com last year and was very happy with the results. BUT DO NOT WAIT until the last minute to use it like I did (April 13 @ 7:00PM), it took 30 to 45 minutes to load web pages. It took me all night long to get my taxes done. My fault for being a procrastinator. It lets you save your session as you use it so you can come back to where you left off if you have to stop and do something else. For the $40.00 I spent, I'm very happy with it. I seem to recall that it saves your taxes in PDF format so you can print them from your computer to send into the IRS.
Taxcut deluxe is only $19.95 and all the app is on your computer. free e-filing and one state return included after rebates. if you don't want the state and e-filing it is only $9.95.
if your taxes are pretty simple, i would think it would be just as good.