I agree that it all depends on who you ask. I had a DTivo DVR for a few year, and I really liked it. But overall I like the R15 better. I prefer the functionality - the integration between live tv and the DVR functionality, e.g. I got my first R15 back in June, and a second one about 2 months later. I've hit some quirks. Some really annoying (first run/repeat issue the biggest of them - which apparently will be fixed in the new s/w release), and some that minor (the progress bar sticking from time to time). Some functionality is well thought-out, but there are some items that make me scratch my head. Again, at least DTV is looking and addressing some of them (e.g. I was always baffled why there was no Series Link manager - but one apparently is included in the next release, and why are new series, by default, given a higher priority over older series? That just makes no sense to me). And one item that the Tivo excelled at, but the R15 requires some work on - consistency of functionality. For example, why can I do a "mark and delete" (very nice functionality, btw) on stuff that's recorded, but not on my to do list? Ditto for the dash-dash to delete?
But then again, there were things on my tivo that made me scratch my head. For example, why in the world can't I do "maintenance" (e.g. getting rid of recorded showings, setting up new season passes...) while watching something? Why no screen saver? That one I NEVER understood - why would you create a box that can pause something on your tv for an indefinite amount of time without offering a screen saver?
Are there issues with the R15? Without a doubt. Has it gotten better over time? Again, no question. It's got issues, but on balance, I wouldn't trade my R15s for a new Tivo unit (I know, that would be considered heresy by many on this forum, but I try to be honest). I just flat out like the functionality better. Has it missed recordings? I think it missed one or two on me over the last 6 months, but I had similar issues with my Tivo. That's not to discount the problems that many have had. Some are serious problems. I've hit none of those. I'm not a power user, but I'm not an occasional user either. I have no problem putting my DVRs through their paces.