I was actually just in contact with them in regards to the E46 M the other day for a different customer. They are currently working on the M kits for both E36 and E46. Both kits are close to completion but their working on a nice feature for the E46 consumers...
According to Solo, there is a substantial amount of customers who are wanting to use a linear type spring in the front as opposed to the progressive rated oem style like most other coilover manufacturers are currently using. This is due to a lot of M drivers are wanting to track their cars and with the linear rate design it makes it easy to swap in and out different spring rates to suit the drivers liking. They are currently testing a simple design that will allow use of a linear spring combined with the factory upper bearing and mount. This design will not require the use of a expense adjustable type mount but they still can be used if the customer desires.
We've obviously become big supporters of these guys over the last year and a half (especially over in the VW community) but it's refreshing to see a company (albeit new and rather small in comparison to the other big players in the marketplace) listening and responding to their customers "wants" and trying to give it to them rather than giving them what they think the customer "needs".... jmo