Your upstream speed matters not at all unless you're either running servers, doing a lot of P2P filesharing, or something like that. For most typical home-user network activities, including gaming, uplink bandwidth is less important than uplink latency, and with FiOS your latency will be minimal.
15Mbps is more than plenty for streaming HD video, so unless you plan on having a lot of people in your place at once, streaming a lot of videos at once, you won't notice much of a difference between the low-end and the high-end for things like watching videos online.
The only place where the higher downlink rates will come into play is (as you say) downloading lots of movies and so forth. But the slow link in that chain is your ability to watch them; if it takes you 5 minutes to download a movie, it'll still take you 2+ hours to watch it, and during that time, another 20 movies could download. So unless you're doing some really heavy-duty stuff, I doubt you'll ever notice a difference between 15 and 35.
That said, the channel bundles are different, too, so if there's a channel you Must Have in the higher package, then you're sorta stuck.
We recently got FiOS for TV/phone (not network1) in the BrokenHome, and we went with the middle channel package, because there were some channels we wanted that the lowest bundle didn't offer. I looked at the super-uber-channels package, and I just couldn't see myself plunking down a monthly premium to have 47 extra channels worth of golf and fishing to choose from. YMMV.
-BP
1 Want to break a Verizon salesdroid's mind? Tell him you want FiOS residential phone/tv service and static-IP network service at the same location.
