Its not bad, mechanized lists are rather hard to make effectively, most especially at lower point totals. You didn't go overboard on upgrades, so that saves me a lot of ranting and nitpicking.

A few suggestions, though:
* This might not be the type of force you're looking for (and if not, feel free to ignore the idea), but a mechanized list can actually be made without using the Mechanized doctrine, and for fewer points. Rather than taking a standard infantry platoon and equipping the command section, minimum two infantry squads, and an additional Armored Fist squad with Chimeras, you can simply take the Grenadier doctrine and take two Grenadier squads mounted in Chimeras. Couple those with your Command HQ mounted in a Chimera, and presto, you've got your minimum requirements for fewer points, you've got better BS for most of your troops, better armor, and more special weapons. The special weapons is a definite plus, because troops scooting around the board in Chimeras won't be able to utilize their heavy weapons as much, making them a costly investment. Whereas you can pile out of a Chimera in rapid fire range and snap off 4 plasma shots per squad.
* An idea for getting additional weaponry without too much expense, is to mount Hardened Veteran squads in Chimeras. That way you can have 3 plasmaguns or meltaguns (for tank hunting) that can rapidly deploy around the board where you need them. Plus they're BS 4 and cheaper than Storm Troopers. A bare bones squad could be nothing more than a Veteran Sarge, 3 vets with special weapons, and a vet with a vox-caster. After they are dropped off or die, you can use a properly equipped Chimera as a medium tank for fire support.
* If you decide to stick with the mechanized infantry platoon, you definitely need to fit some special weapons into your infantry squads. They give your squad added punch and you can always use them on the move. The same can't be said for heavy weapons.
* Finally, I'd suggest changing one of the Demolishers to a a basic Leman Russ (and maybe drop the hull-mounted lascannons on the regular Russes for heavy bolters). Two Russes and a Demolisher or Basilisk gives you good mobile, long-ranged firepower and gives your opponent a bigger headache by having to take out two of them.

 

A couple of things I would change:

1> Add smoke launchers to all Chimeras. Most important tank upgrage IMO. If you aren't planning on driving up to the enemy, drop the Extra armor.

2> With the Chimeras, you have plenty of anti troop firepower. I would change the Heavy bolters and Missle Launchers in the troop squads to Lascannons. IMO all IG armies NEED 4 of these somewhere, especially if you don't take some DS Stormies with Melta Guns.

3> To make up the points for the Lascannons, I would change one of the Demolishers to a Bassilisk. That is my favorite Heavy Support combo: Russ, Bassie, Demolisher.