First Bike purchase for trail riding

[BUGZs15]

Hi,

I have recently started mountain biking and have only had experience at Manly Dam trail, I have been 3 times and usually hire bikes at Manly.
I love the thrill it gives me and want to go more often.
I am currently searching for a MTB to ride some of the trail around Sydney, with main one being Manly dam.

I am looking to purchase a bike to learn on and have come across this model(I know of this model as this is what i have been hiring at Manly Cycles)

POLYGON XTRADA 5.0 Shimano Alivio 27 speed

KEY FEATURES

Full 27 Speed Shimano Alivio componentry throughout (new 2012 rapid fire +), giving you all the gears you need to tackle any terrain.
Tektro Aquila Disc brakes for dependable stopping power and easy maintenance.
Magnesium, Hydraulic Lockout forks, which are lighter than Aluminium and provide better control.
T6 Aluminium frame with oversized seat post and headset, is lightweight and stiff, giving a responsive ride.
Alloy handlebar, stem and seatpost deliver strength, style and performance.
Selle Royal italian saddle and cushioned rubber grips enhance your comfort.
Polygon Siren double wall rims with Kenda Kharisma tyres offer a well-balanced combination of easy-rolling performance and confidence-inspiring traction.
Weight = 12.5kg (+/- 0.2kg)
5 Year Warranty on Frame.
2 Year Warranty on Parts.
FREE 14 day test ride - click here for more information.
FREE Delivery Australia Wide.
http://www.bicyclesonline.com.au/polygo ... -27-speed/

It has pretty good specs for the price the only thing i am not unsure of is if this is a good bike for the money.
I do plan to upgrade in a couple of years if i take it more seriously, but do wish to learn on something cheaper.
Would anyone be able to provide some feedback if this is a good bike to purchase and what sizing should i get, I am 182cm tall.

If there are other worthy bike for similar price range, please let me know.

Cheers

[zero]

At that price its a reasonable deal.

I don't think the new 9 speed alivio is as bad as old 8 speed alivio, though I would personally stick to the deore or the equivalent SRAM group for manly - been caned too many times by old alivio deraileurs breaking to want to try it again, and I've had good reliability from the non wearing deore bits (derailuers/shifters etc).

Some of their claims regarding similar quality to the trek 4500 have to be taken with a grain of salt - particularly the accessories and wheels. Not enough to cover the price gap between 4500 not on special and this bike on special though.