I first tried an aluminum "V" block bedding system on a Remington 40x in about 1977. It worked reasonably well but not as well as the glass bedded stock which followed. I have built a few rifles with machined aluminum blocks over the years and they worked well. These were all glass bedded over the aluminum, however.
I'm not a huge fan of the aluminum pillar except in certain cases. Mostly, I consider glass pillars to be as good or better.
The material used for the stock itself has much to do with the bedding system used. A plastic stock with the aluminum block molded right into it seems like a pretty good system. At least you can bed the aluminum. Fiberglass stocks with a good, solid action section don't require or benefit from aluminum pillars or blocks.
I once bedded a Shilen DGA action on a pair of 1 1/8" steel pillars. The pillars fit beautifully and I had high hopes for the system but it wasn't that great. I ended up dumping the pillars and gluing it in and it worked fine.
My preference is to pour glass pillars in any wood stock or any glass stock which is insubstantial in the action area. I like to use aluminum or steel where the surface is limited (Mauser tang). Regards, Bill