2007 Mazda 6 Transmission issue shifting from 3-4

I'm looking at purchasing a used 07 mazda 6 from a friend. They are making me a very good deal on it. The only issue is that after the car gets warm, sometimes the shift between 3 and 4 is harder than normal. It happens more if you put your foot in the gas, but it doesn't happen always.
I've done some reading around the web and seen several other forums where people are complaining of the issue. I've seen the TSB that Mazda put out regarding it. The "fix" for the issue is a new transmission. What I can't seem to find an answer for is whether or not this issue is "fatal" to the trans, or just an annoyance? Any of you guys have this issue with your mazda 6's ? If so how long did you/have you driven it with this issue?
Thanks!

Good friend or good deal I'd walk away. The problem probably requires a tranny replacement, ( mileage on an 8 year old car). If you're getting an excessive 3-4 shift shock when driving on an uphill road or with some load applied. Due to uneven wear on the servo piston bore , oil leakage from the bore occurs. This in turn causes a mistimed engagement of the 2/4 band , resulting in the 3-4 shift shock. To correct the problem, the servo piston has to be replaced with an updated piston and possible sleeve of correct hardness. This along with the cars mileage would require an overhaul.

I wouldn't bother with it. If you still want to go with it, take it to the Mazda dealer service center and have them check it out before you purchase the vehicle.