I know exactly what you mean. For all purposes in figuring out "teh", etc, I find urbandictionary very helpful - also helpful are 1337 and
lolspeak guides - did you even know there is a bible translation process into lolspeak? (... n den teh cieling cat ... )
I really do prefer it when people type out their sentences properly but I can definitely understand using abbreviated forms "no u go ovr der NAO" like when you are playing tf2 and do'nt have time to type properly.
In a normal conversation though it is just plain annoying and I will actually switch from proper grammar and spelling to their ... obnoxious ... speak when they start speaking it as a silent and somewhat odd joke.
like ...
"hey dude what's up"
me: "hey man hows it going"
"hai d00d was hapn"
me: "OMG HWOS I FSIH 4 TEH MINEZ!?!"
"O_O"
me: "SPIEHS SAPN MEH SENTYIES! GOM GOM !!!one!11!!"
"kbai"
me: "thank god..."