Down but not out said:
The 7M gets a bad rap, but in reality its no less reliable than a J series engine. Poor rebuilds, zero maintainance and cheep kids wanting more boost rather than spending the money on reliability are what bring the engine down and give it a bad name.
Look, I love my 7m and don't have any plans of swapping to something different. But, the 7m has had problems from day one back in 1986 (as far as the MKIII is concerned).
Out of the box, it is less reliable than a 2j (don't know much about 1j's). I had my first Supra back in 1995, when some of these MKIII's were still in warranty. The headgasket problem was a known thing. There were calls to get Toyota to perform a recall because of it. Somehow, Toyota escaped and what remained were a bunch of MKIII's running around with what was really a known defect; namely, the torque specification of headbolts.
A significant percentage of these cars have had BHG's. If someone buys an older car and romps on it - they should know they are running a higher risk than with most vehicles.
The 7m has now been proven to be reliable if rebuilt properly and with attention to detail. Don't blame all of the 7m's image woes on teenagers who are not taking care of their vehicles - while abuse certainly never helps a vehicle, it does not mean that the specification flaw is not there.
I think it easy for us to forget how old these cars are getting - they may age gracefully, but let's not forget the 7m's have had the chance to age a bit more than 2j's.
Bottom line - the 7m is a great engine. I personally see no reason for the expense or time of a swap unless you're really looking to put some serious numbers to the ground. But that does not change the fact that a 2j is indeed a more reliable and better designed motor.