There's a whole gamut of stories about going into Cambodia, but I would just like to make sure that crossing into Thailand is easy/scam-free.
Is there anything to careful about (fabricated charges..) .. and how much is the standard fare to get a driver to go to the border from Poipet/ border to Aran..?
Thanks in advance.

No problems going back. Usually you go through the checkpoint and walk to the shops where your bus is waiting to take you to Bkk. I have found it to be included in the initial bus price which can be around $10.Check out www.talesofasia.com for any info on going back.

Much easier.
how much is the standard fare to get a driver to go to the border from Poipet/ border to Aran..?
60B
where your bus is waiting to take you to Bkk.
And waiting, and waiting. I find the independent route more satisfying.

Crossing into Thailand is not without its hazzards and it doesnt matter whether you are travelling in a pre-arranged way or independently. This is a border crossing in developing countries .. there are always going to be people who are struggling to live trying to earn a living from people who present a business opportunity.
What ever way you have arrived in to Poipet without any means of onward travel to BKK you will walk over the border to the market. 60 - 80 baht would be a reasonable price to pay a tuk tuk to the bus stop in Aranyaprathet where you will find that that will be a bus leaving for BKK about every 30 minutes or a bit longer depending on the time of day.

I paid 50 baht for a tuk-tuk from the border into Arunyaprathet, to the first class bus terminal. The bus to BKK was about 250 baht.
Don't understand why people quote prices in dollars in Thailand...
This was 5 months ago.

Hey man just walk. The authorities won't let you get too far away from where you should be, and to get from Cambodian customs to the bus terminal on the Thai side is too short a walk to get a tuk tuk for.

5 Baht for the share taxi and normally around 205 baht to Bangkoks northern bus station by bus

The problem you will get is the queues at immigration going into Thailand as they can be very long at certain times of the day.
I recommend you take a taxi to Poipet early in the morning so you miss the queues at immigration.
Once you get past immigration then just look for a tuk tuk to take you to Aranya Prathet and it should cost between 60b to 80b.
More info here

to get from Cambodian customs to the bus terminal on the Thai side is too short a walk to get a tuk tuk for.
You're getting something else confused with 'bus terminal' here. Aranyaprathet is at least 5km from the border.

#7 & #8 - There is VIP buses which leave from just outside the car park near the actual border crossing. They cater primarily to Thai's having a day out at Poipets casino's (or at least the Pattaya bus I jumped on did). It's a cost effective way to get to Bangkok or Pattaya when you remove the cost of a tuk tuk to the main bus station. The bus to Pattaya was 300 baht & I THINK to Bkk 200 to 250 baht depending on whether it was a mini bus or big luxuary coach.