3x3x3:
Anything above 15 is unsatisfying, but some 15.xx are not average-destroying. However, I still don't hit sub-12 often, so anything lower is great.
4x4x4:
Sub-1 is good, sup-1:10 is despicable.
5x5x5:
Sub-2 is fantastic, and I start getting grumpy after 2:15
BLD:
Sub-1:10 is good, sub-1:20 is decent, and sub-1:30 is okay for slow practice.
OH:
Sub-25 is a very clear line of okay-ness. Sup-30 is unacceptable.
Let's see... For me a nice smooth solve with good look ahead and few cube rotations is a good solve. The times for these are normally around 15 seconds. I think anything sub16 I'm happy with, and I average 19ish seconds with a PB average of 12 of 18.65 seconds.
For OH I like anything sub30. PB average 34.xx (something).
For 4x4x4 anything sub1:40 would be great right now, although I know that as soon as I stop using my stiff cube my times will drop like a stone so I'm not really satisfied with any 4x4x4 times at the moment.
For 5x5x5 I aim for sub3, but I have never really been satisfied with a 5x5x5 solve as of yet. Still wating on sub2...
<20...HECKYES
<23...cool
<25...I made some mistakes 0...O_o something happened
<40...POP or cubing-halfasleep
<50...I have an emergency noose for situations like this
20+: pop, or wrong cross, or something weird
19: what happened?
18: mistakes or using old style wristy kind of moves during F2L rather than fingers (trying to break my bad habits)
17: mistakes
16: meh...
15: good but not great, bad but not that bad. I don't like 15's because I want to get faster on average, and this has been my average (at home) for years now
14: there we go
13: now that's what I'm looking for!
12: great solve!
11: awesome solve! (probably only get 1-2 of these per day)
10: This just totally makes my day, I only get these maybe once or twice per week
sub-10: still dreaming of this for a non-lucky solve.
Well this is what makes me feel like it was a really good solve:
2x2: Sub-5 solve
3x3: Sub-15 solve
3x3OH: Sub-25 solve
4x4: Sub-55 solve
5x5: Sub-1:45 solve
3x3BLD: Sub-DNF
I haven't gotten an average of 12 under any of these except the OH, so they're generally better than average.