My power went out, so I took a while to respond.
I haven't noticed a substantial heat increase. It's tough to be precise because I forgot to record my CPU temps prior to the upgrade. My wife's similar Dell 1505 that uses a T2250 hits 78C on LinX. Mine hits 88C now and has slightly worse vents for a similar heatsink. That leads me to believe that my original CPU hit maybe 80C on LinX before and 88C now--so no big heat increase. Tjmax is 100C for this CPU, by the way.
Old Max: 80C
New Max: 88C
The new good thermal compound (Tuniq TX-2) may also dissipate heat better than the original compound.
Keep in mind that LinX causes higher temps than pretty much any real world CPU intensive operations will cause. Also, I live in Guam and don't usually have air conditioning so the humid tropical air bumps my temps up about 10C or so.