We used PayPal for a year but we have switched to Realex in the last few months.
Initially we looked at World Pay, but they were very expensive to set up, and their transaction charges were much higher than Paypal, so we decided to go with Paypal.
We bought a book called "PayPal Hacks" on Amazon and found this extremely helpful when setting up our website. It explains how PayPal works, and shows you many shortcuts to make it easier to implement.
We used Paypal for just over a year, but we decided to move to Realex because of the following;
1) While PayPal does not require your customers to set up a PayPal account, we found that customers found the screens confusing and many of them believed that they did indeed have to open a PayPal A/C. This put some of our customers off, or just confused the hell out of them
2) PayPal deducts its transaction fees directly from each transaction. This creates a lot of work from a VAT point of view, as you are liable for the VAT on the amount before the charge. If you are accounting for VAT on a Cash Basis this can cause a lot of work for you. Also, PayPal does not issue you with a bill as such, so you have to account for the transaction charge to keep things right.
3) PayPal does not issue you with any paper statements. You can download your transactions electronically. The problem here is that if you had an Audit you could end up with a hard time trying to prove to the Auditor that you have not accounted for all the money - you have no independant paper to prove otherwise.
4) If your customer used their credit card previously with paypal, and created an account at the time, but no no longer remembers the password then PayPal will not let you process the transaction because the credit card number is already associated with a PayPal account, and insists that your customer logs in.
5) For security reasons PayPal requires the user to enter a lot of information - Name, Address etc along with the standard Credit Card Details. While this is mostly a good thing it really slows the user down. Also, they expect the address in a format very similar to the US or UK idea of ZIP codes or Postal Codes. This really slows the customer down.
We have since opened a Merchent Account with EuroConnex, and use Realex to process the transactions.
The advantages are;
1) Their rates are actually lower than PayPals in a lot of cases
2) They will accept Laser Cards. Laser cards are great as a lot of business customers prefer them, and the transaction charges are fixed at 20 cent irrespective of the transaction amount
3) Both Euro connex & Relaex present bills for the transaction charges on a monthly basis and Direct Debit your own bank account. This solves the VAT issues I mentioned earlier.
4) The money automatically comes into your bank account from your merchent account on a daily basis (but 3 days behind)
5) You receive proper bank statements for the Merchant account - you can stand over your accounts.
6) Your customer only has to enter Name, Credit Card No, CCV code and Expiry Date - very quick
The only advantage that PayPal has over Realex is that PayPal do not have a minimum monthly charge - you pay noting if you sell nothing.
With Realex you have a minimum charge, but it covers you for a block of transactions, above which you pay per transaction.
That all said, we are much happier with the Realex solution