We stayed for two nights at The Marlborough. The staff were very good - courteous, helpful, informative, fast.
The room itself was very disappointing. The bed was uncomfortable and felt old. The bathroom was very small and tired. The carpet was old. The TV was the smallest I have seen for a while.
Having said that, it was clean.
I did not see any other hotels in Shanklin but really cannot imagine the Marlborough is the best for the price.