I've had my 300 for just over a year now and it still surprizes me, running v3.5 at the mo.
Im using the Duracell Recharge 1800 mAh, Bought the 4 batts with charger in one, always better to have the extra batteries with you in the mountains. One set will last you more than a day if you not chasing nums an pulling all the info off your 300, changing profiles.
What type of accessories are you after?