Sightspeed did recently double the fee, which we weren't thrilled about. Each of our subscriptions has since run out, so we're both on the free version, me for one session, my player for two. Admittedly small sample, but we haven't seen any difference so far. If we needed the (new) four-way feature we'd pick the paid version back up, but right now it's just the one player. Sightspeed updates several times a year, and there's been a dramatic improvement over the years in the quality of service.
Aural quality tends to be much better than visual. It's good enough that the remote player can take notes for the session writeup, hear conversations in the next room, and we have no more problems than a typical cell-phone conversation. Paradoxically, we find the aural works better if we have the settings intuitively reversed - he's in a noisy place (wearing ear-buds) and we're in a quiet place.
Video, OTOH, is less consistent. Colors are a bit washed, there's some pixelation, and occasionally it will pop out of full-screen to a reduced mode. It's a bit like an older VHS tape. I should note we both have cable internet - don't try this with less than DSL! Also, on my end, the server is an iSight camera attached to a 2003 Mac with a 867MHz G4 processor - performance would no doubt improve if a more modern machine were used. My player is using a roughly two-year old PC, not sure which brand.
In terms of the remote player's involvement, he's the party leader, which I think says it all. It does add to the banter. Some days we accuse the remote player of appearing "almost life-like" and threats of bodily injury to someone 1000 miles away ring a bit hollow.